Method of making steel



Patented June 13, 1939 2,162,437

UNITED STATES PATENT OFFICE 2,182,437 METHOD OF MAKING STEEL Clarence D. King, l lrooklyn, N. Y.

No Drawing. Application December 22, 1931, 'Serial No. 181,227

Claims. (CI. 75-28) This invention relates to methods of making naces for the purpose of producing an iron high steel. One of the objects is to provide an imin phosphorus, above 31%; and high in mangaproved process for making steel. Another object nese, above 5%. If the use of open hearth slag is to provide a more economical process for makdoes not assure sufllcient manganese and phos- 5 ing steel than heretofore practiced in the art. phorus, the additional phosphorus may be built Other objects and advantages will be apparent as up from phosphate rock or high phosphorus ores the invention is more fully disclosed. or high phosphorus manganiferous ores.

in the manufacture of steel by the basic open \A comparison of standard basic iron burden hearth methods common to the art, relatively and a typical burden required for the high phoslarge volumes of slag are produced. These slags phorus high manganese iron is, as follows: 19

contain various amounts of iron and manganese oxides, and of phosphorus compounds. Other sm-ndBr-d b'asic High phosphorus, constituents of the slag are calcium oxide (or iron (pounds per p fl gf lime) and'silica. The iron, manganese, phos toil-the?" phorus and lime content of the slag represents M 15 economical values too useful to be discarded, but 3,112 2 e31 heretofore in the art no economically practical method for the complete recovery and use of 406 2.000 these constituents has been proposed. 33g 2 In accordance with the present invention, I 2 propose to utilize the open hearth slag as a comi fg ggff 292% 1.02% ponent' of the usual charge in a blast furnace, Manganese 2.36 7.50 regulating the proportion of constituents in the blast furnace Charge 50 that a p iron contain- The second step consists of using an acid Besse- M'. ing high p phorus and high mang e is mer converter to blow said iron, all the phostailled- Y high Phosphorm3 is meant Over 50% phorus of the iron being retained in the blown and by high manganese ismeant Over metal since the acid process does not permit the I then D 019059 to blow this P first elimination of the phosphorus, an virtually all in an acid Bessemer furnace to convert the Si and the manganese and Silicon being oxidized d Mn Content thereof oxide- The silica carried into the slag. For example, the follow- 30 games? oliidestogether with such oxides ing represents an actual test blowing of iron oi formed during the blowing of the pig iron form this character in an acid v t 3. slag which is separated from the P-containing iron. I propose to return this slag to ablast fur- Analysis of pig iron: cent 35 nace wherein the Mn content is recovered by calfbon 35 being again reduced andconverted into silicon- Manganese spiegel in which form it may be utilized as Mn Sulphur additions to molten iron or steel baths replacing Silicon equivalent amounts of term-manganese. The Analysis of blown metal- 33 40 P-containing iron from the acid Bessemer is then Carbon -31 I treated with a basic oxidizing slag, preferably in Manganese a regenerative furnace, which slag rapidly abstuphur stracts or removes the phosphorus from' the iron smcon '7 forming a slag adapted by reason of high Analysis of final slag- 34 10 5 phosphorus content for use as a soil conditioner. Sioz After separating the P-containing slag froni the 64 molten iron the iron may be 'i'urther 58'10 accordance with standard practice under-3%; sec nd bas c oxidizing -8 until the 18113611 and It will be noted from the above analysis that phosphorus content s been ed the the extremely high manganese content of the pig m sired Percentage and t e desired fi flt iron materially assists in desulphurizing the position is obtained. blown metal, which is, a collateral value of the Referring to the Process in te tafl. the process since the use of such high manganese is first step in the process consists in thense of very not ordinarily possible or practical in steel prolarge amounts of open hearth slag in furduction. It will also be noted that the manganese is virtually eliminated fromthe blown metal and transferred to the slag in the form of manganese oxide as high as 58.10%. While those familiar with the art have questioned the feasibility of blowing high manganese iron, I have demonstrated that this can be accomplished practically.

The third step of this process is the reduction of the Mn-containing slag in a blast furnace to form silicon-spiegel by well known practice, which can be regulated to produce from this slag as part of the burden a silica-spiegel of 10-20%, or more, of silicon and 20-40%, or more, of manganese. This silico-spiegel may be substituted for appreciable amounts of ferro-manganese and silicon now required in steel making operations, result ing in a material reduction in the amount of foreign high grade manganese ores now required to produce standard ferro-manganese. This is a particularly valuable feature in the event that high grade manganese ores are difficult to obtain from foreign sources'for one reason or another.

The fourth step in the process is to use the high phosphorus blown metal resulting from the second step to form a high phosphorus slag adapted for use as a soil conditioner. The blown metal is placed in a tilting open hearth furnace together with roll scale or other forms of iron oxide, and

v limestone, or other forms of lime to form a basic oxidizing slag which combines with the phosphorus content of the blown metal. The resultant P- containing slag is separated from the metal, and ordinarily such slag will contain 12%, or more, P205 and, therefore, is highly suitable for soil conditioning purposes. The remaining slag on the metal is diluted by additional lime and the steel is further refined and finished in the usual manner, until the final desired composition is obtained. By the practice of this invention I may obtain a low phosphorus, low sulphur open hearth steel if desired. From the above description of the present invention it is believed obvious that the process has specific economies and advantages over present-day methods, which may be enumerated as follows:

1. Replacement of appreciable amounts of limestone and ore in blast furnace burdens by lime, manganese and iron now wasted in open hearth slags.

2. The recovery of the phosphorus content of open hearth slags in a useful form-soil conditioner.

3. The recovery of the manganese content of the open hearth slag in a useful formsilicospiegel.

4. A reduction in the amount of ferro-manganese and a collateral reduction in the amounts of foreign high-grade manganese ores required in the manufacture of steel.

5. The economical production of unusually low sulphur and standard phosphorus content of basic pen hearth steel.

, following claims:

What I claim is:

1. In the manufacture of steel comprising the steps of producing in a blast furnace a charge of pig iron, blowing said pig iron in an acid Bessemer converter, and refining the blown metal in a basic open hearth furnace, the improvement which comprises adding to the usual charge ontering said blast furnace sufficient phosphorusand manganese-containing slag materials to introduce in said pig iron a manganese content exceeding 5.00% and a phosphorus content exceeding .70%.

2. The process of claim 1, wherein the slag resultant from the blowing of said pig iron in an acid Bessemer converter is returned to a blast furnace and the manganese content thereof recovered therefrom as ferro-manganese, spiegel or pig iron.

3. The process of claim 1, wherein the blown metal is first treated with a basic oxidizing slag to remove therefrom the bulk of the phosphorus forming a phosphorus-containing slag suitable for use as a soil conditioner and the remaining metal refined to the extent desired under a second basic oxidizing slag to produce a steel of the desired composition.

4. The process of claim 1, wherein the phosphorusand manganese-containing materials added to the charge in said blast furnace is comprised at least in part of open hearth slags.

5. A steel making process comprising producing in a blast furnace a charge of pig iron containing over Mn and over .70% P by adding to the usual burden sufficient phosphorus and manganese-containing slag materials to provide the additional manganese and phosphorus re quired over that of ordinary pig iron, blowing the pig iron in an acid Bessemer converter to remove therefrom the carbon and to convert the silicon and manganese content into an oxidized slag, separating the said oxidized slag from the metal, recovering the manganese content of said slag by utilizing the slag as part of the burden in a ferromanganese blast furnace, treating the Mn-free blown metal with a strongly basic oxidizing slag to remove the bulk of the phosphorus content therefrom and to form a P-containing slag suitable for use as a soil conditioner and treating the remaining metal with a second basic oxidizing slag to remove the balance of the phosphorus and other impurities to the extent desired in the forming of a steel of desired composition.

CLARENCE D. KING. 

